Slide 21

Extracellular single unit recordings from cortical neurons in anesthetized animals have been used to examine the effects of blocking out the cells classical receptive field (while still stimulating the surround) on the size of this receptive field (represented in top left). Plotting the amplitude of evoked response versus the distance from the center of the receptive field indicates that following the artificial scotoma, the response of the cell is increased at all locations, and there may be an expansion of the receptive field.

However, in a study by DeAngelis et al. (bottom traces) the authors present evidence that this effect is mediated mainly by a change in the gain of the cell, with little change in the size of the receptive field (see publications listed below).

We hypothesized that adaptation, and its movement of the membrane potential, may underlie at least part of these effects on visual receptive field strength and structure.

The top Figure is from: Pettet, M.W., and Gilbert, C.D. (1992) Dynamic changes in receptive-field size in cat primary visual cortex. Proc. nat. Acad. Sci. USA 89: 8366-8370.

The bottom Figure is from: DeAngelis GC; Anzai A; Ohzawa I; Freeman RD (1995) Receptive field structure in the visual cortex: does selective stimulation induce plasticity? Proc Natl Acad Sci U S A 92:9682-9686.